The present invention relates to a device for mounting and dismounting of a probe in process pipelines, tanks etc., as well as a probe accommodating arrangement.
Several suggestions exist for mounting and dismounting probes in process pipelines, tanks etc. Such probes are used for measuring corrosion, pressure, temperature etc, inside a system, such as in oil, gas and process industries. With a nipple, a probe can be mounted through a hole in the equipment into a tube to contact the medium of the process.
The mounting and demounting of probes is preferably conducted at normal operating conditions, which means that the system is not shut down when probes are to be changed or inspected. In connection with process a pipeline, this means that the normal operating pressure is maintained, and that draining of fluid/gas will not be necessary. This means a substantial reduction of the maintenance costs.
The disadvantage of prior art hydraulic and/or mechanical retrievers is the risk of leakage upon the mounting and demounting of the probes. This may be detrimental to the environment.
In the offshore oil industry, process pipelines and transport pipelines are placed on the sea bottom. The condition for such pipeline needs surveillance and probes have to be mounted and demounted for maintenance and upgrading. For various reasons it is desirable to use remote operated vehicles (ROVs) to conduct this operation. The depth of the sea bottom may make the use of divers dangerous and even impossible, and it is more economical to use a ROV. The security of such work has to be high, as a leakage can have large economic and environmental consequences.
Prior art technology is largely based on mechanical operations, such as use of threaded connections between a retriever and the probe and between an access tube and the retriever, and use of mechanically operated handles for opening and closing valves. Such mechanical operation can be difficult to accomplish by a ROV.
Efforts have been made to reduce the number of operations and to replace some of the threaded connections with simpler mechanisms. U.S. Pat. No. 3,589,388 (Haneline, 1971) shows a pressure operated retriever for withdrawing an injector nozzle from a high pressure environment. This structure comprises a ball valve which in its open condition has an opening for introducing the injector nozzle. Further it comprises a partly hollow or tubular connection device with two or three grooves for defining a plurality of fingers. A radially protruding tongue is arranged on each finger to be accommodated in an opening behind an injector needle. The fingers are resilient to enable connection to the opening. The probe can be pulled out by the retriever due to this connection,
A disadvantage of this retriever system is the need for a screw connection radially to the access tube to fasten the injector needle. The connector device can only be pulled out of the opening without the injector needle when the screw is tightened.
U.S. Pat. No. 4,275,592 (Atwood et al, 1981) shows a retriever utilizing fingers with lips to pull a probe. A number of threaded connections are shown. This retriever will not be suitable for exchanging probes in sub-sea pipelines.
U.S. Pat. No. 4,002,059 (Jeffers et al, 1977) shows a retriever for mounting and demounting of probes with corrosion coupons in process pipelines. During operation, the probe is locked in grooves in the access tube by spring-loaded locking means on the probe. The retriever can be lowered over the probe by a wire comprising a grappling means and a rod-like body. As the retriever is lowered over the probe, the rod-like body is lowered through an opening in the upper part of the probe to release the spring-loaded locking means. The grappling means comprises arms catching a circular groove at the top of the probe, before the probe can be lifted from the access tube.
The disadvantage of this retriever is the need for two different tools for mounting and for demounting the probe. Additionally, a weight and wire are used for lowering and pulling the probe. Neither of these arrangements will be suitable for ROV operation.
From Norwegian patent specification 317390 (CorrOcean, 2004, and corresponding to U.S. Published application 2006/0123933), a device for mounting a probe in a process pipeline or a process tank is known, which device is not provided for remote operation by an ROV.
From PCT Application WO2006/1 18471 (CorrOcean 2006), a device for mounting and demounting of a probe is known, which is arranged in an access tube to a process pipeline and/or a tank. This device requires a valve housing with a ball valve with opening for handling of the probe at mounting and demounting.